This invention relates to an automatic document transportation device for a copier and the like for transporting an original document sheet to its scanning position to have its printed surface optically scanned and to a discharge location after it is scanned. More particularly, the present invention relates to a mechanism in such a device by which the motion of the sheet can be switched between a supply route for transporting it to the scanning position and a discharge route for removing it from the scanning position.
An automatic document transportation device is typically provided opposite to a document table (for example, of a transparent glass material) of a copier and serves to automatically transport an original to be copied onto the table and discharge it after it has been processed. In general, many document sheets are stacked on top of a document supply table and they are transported onto the table one sheet at a time in response to a control command from the copier. After each sheet is moved to the scanning position and optically scanned, it is discharged into a discharge tray and the next sheet on the supply table is transported onto the table.
An automatic document transportation device of the type described above is generally provided with a conveyor belt disposed opposite to the document table for transporting the document to the designated scanning position on the table. In order to bring the document sheet accurately to the scanning position, the driving force adapted to keep the belt traveling at a constant speed is switched off before the document sheet reaches the desired position (or before the front edge of the sheet reaches a stopper or the like) such that the belt travels an extra distance by inertia, causing the front edge of the sheet to gradually come into contact with the stopper. After the document sheet thus brought to the desired scanning position is scanned and is about to be discharged into the discharge tray, a solenoid or the like is activated to move the stopper from its earlier position such that the front edge of the sheet is no longer stopped thereby and that the sheet can be moved again towards the discharge tray.
Japanese Patent Publication Tokkai No. 60-19134 has disclosed, by contrast, a different kind of automatic document transportation device which, after a document sheet is scanned at the scanning position, transports the processed sheet backward in the direction from which it has been brought in. The path from the supply position to the scanning position and the path therefrom to the discharge tray are switched from one to the other by changing the position of a guide piece.
With a conventional automatic document transportation device of either type described above, a solenoid or the like is required to drive the stopper or the guide piece to select a transportation route. This has the disadvantage of making the circuit more complicated.